Rapid Prototyping and Rapid Tooling Development

Knowledge sharing by Guangdong Shunde Teamwork Model Technology Co., Ltd, whom with over 20 years rapid prototyping experience.

Email: ken@gdtwmx.com

Website: www.gdtwmx.com

This article reviews the development of rapid prototyping technology, especially the recent achievements in rapid prototyping systems, materials, and rapid tooling, and analyzes the trends in rapid prototyping and rapid tooling.

1 Introduction

The 21st century is characterized by the knowledge economy and the information society. The manufacturing industry faces the severe challenge of the rapidly changing market in the information society for the requirements of multiple products in small quantities. With the increasingly internationalized manufacturing industry, shortening the product development cycle and reducing the risk of developing new product investment have become the key to the survival of the company. The rapid prototyping technology for generating three-dimensional objects directly from computer models has emerged from the rapid development of modern design and modern manufacturing technologies. It involves mechanical engineering, automatic control, lasers, computers, materials and other disciplines. In recent years, The technology has been rapidly applied in industrial modeling, manufacturing, architecture, arts, medicine, aviation, aerospace, archeology, and film and television. Rapid prototyping / rapid prototyping / rapid manufacturing technology provides an advanced means for companies to improve their competitiveness.

Rapid prototyping (RP) has been a major advancement in forming systems and materials since the 80s. It has also promoted rapid tooling (RT) and rapid manufacturing (rapid manufacturing). The development of the following RM), the mid-to-late 90's is the period of rapid development of RP technology.

China's Huazhong University of Science and Technology, Tsinghua University, Xi'an Jiaotong University, Beijing Longyuan Company and Nanjing University of Aeronautics and Astronautics, etc., took the lead in the early 1990s to develop the research, development, promotion and application of RP and related technologies. By 1999, dozens of imported or domestic RP systems had been operating in enterprises, universities, research institutions, and rapid prototyping service centers in China. Under the leadership and support of the Ministry of Science and Technology, nearly 10 "rapid prototyping manufacturing technology productivity promotion centers" were established to promote the use of RP technology. The 863/CIMS subject-matter expert group also incorporated rapid prototyping technology into target product development projects. In addition, a considerable number of universities include RP technology in the "211" plan. The number of units investing in RP research in China has increased year by year, and the RP market has taken shape.

2. Brief history of rapid prototyping technology development

The RP technology is a manufacturing method in which materials are deposited layer by layer or point by point. The idea of layered manufacturing of three-dimensional objects first appeared in the 19th century when manufacturing technology was not developed. As early as 1892, Blanthre advocated using a layered approach to make three-dimensional map models. Professor Niekawa Nakagawa of the University of Tokyo in 1979 used metallurgical techniques to manufacture metal stamping dies, forming dies, and injection dies.

The development of lithography has played a catalytic role in the emergence of modern RP technology.
From the late 1970s to the early 1980s, Alanj. Hebert (1978) of the 3M Company of the United States, Xiao Yuxiu Male (1980) of Japan, Charles W. Hull (1982) of the U.S. UVP Corporation and Maruguchi Yoji (1983) of Japan, were Different locations have independently proposed the concept of RP, namely the use of successive layers of solidification to create new ideas for three-dimensional entities. Charles W. Hull, with the continued support of UVP, completed a project called Sterolithography that can automatically build parts.
The complete system SLA-1 of the Apparatus (SLA), which was patented in 1986, is a milestone in the development of RP.

In the same year, Charles W. Hull and the shareholders of UVP established the 3D System company; many of the concepts and technologies related to rapid prototyping subsequently developed in 3D System. At the same time, other molding principles and corresponding molding machines have also been successfully developed. In 1984, Michael Feygin proposed a method of Laminatde Object Manufacturing (LOM) and formed Helisys in 1985. Before 1990, the first commercial model LOM-1015 was developed. In 1986, C.Deckaed, a graduate student at Exas University in the United States, proposed the idea of Selective Laser Sintering (SLS). Later, he organized the DTM company. In 1992, SLS-based commercial molding machine (Sinterstation) ScottCrump was proposed in 1988. Fused Deposition Modeling (FDM) thought, in 1992 developed the first commercial model 3D-Modeler. Since the development of SLA optical molding technology in the mid-1980s to the late 1990s, more than a dozen different types of rapid prototyping technologies have emerged. In addition to the aforementioned types, 3DP, SDM, and SGC are also typical. At present, the four technologies of SLA, LOM, SLS, and FDM are relatively mature.

3, the new progress of RP technology

3.1 Photocuring (SLA)

This forming method is currently a kind of rapid prototyping method with the most in-depth research, the most mature technology, and the most extensive application in the world (see Figure 1). Currently studying SLA methods are 3D System, EOS, F&S, CMET, D-MEC, Teijin Seiki, Mitsui Zosen, Xi'an Jiaotong University, and Huazhong University of Science and Technology. US 3D System’s SLA technology accounts for the largest proportion in the international market. After its SLA-250 model was introduced in 1988, the SLA technology has made great strides in technology. In recent years, SLA-3500 and SLA-5000 machines have been introduced. The use of semiconductor-excited solid-state lasers results in scan speeds of 2.54m/sec and 5m/sec, respectively, and a molding layer thickness of at least 0.05mm. The SLA-7000 model introduced by the company in 1999 is comparable to the SLA-5000 model. Although the molding volume is approximately the same, the scanning speed is 9.52m/sec, the average forming speed is increased by 4 times, the forming layer thickness is at least 0.025mm, and the precision is doubled.

There are four major series of SLA molding technology materials: Cibatool SL series produced by Ciba, SOMOS series from Dupont, Stereocol series from Zeneca, and RPCure series from RPC (Sweden). Cibaool SL series has the following new varieties: Cibaool SL-5510 for SLA-3500, this resin can achieve higher forming speed and better moisture resistance, as well as better forming accuracy. Cibaltoo ISC-5210 is mainly used in environments that require protection against heat and humidity, such as underwater operating conditions. The SOMOS series also has a new type of OMOS 8120. This material is similar in performance to polyethylene and polypropylene and is particularly suitable for making functional parts. It also has good moisture and water resistance.

Japan has broken the convention of using SLA technology to use UV light sources. Under the cooperation of Nippon Kayaku Co., Ltd. developing a new type of photosensitive resin, DENKEN ENGINEERING and AUTOSTRADE have taken the lead in using semiconductor lasers with a wavelength of around 680 nm as the light source, greatly reducing the price of SLA equipment. . In particular, AUTOSTRADE's EDARTS model uses a constrained liquid-type structure with a light source radiating from below through a layer of glass (see Figure 2), making the device price down to 2.98 million yen. Xi'an Jiaotong University has launched LPS and CPS series SLA molding machines and corresponding photosensitive resins. The CPS molding machine uses a UV lamp as a forming energy source.

3.2 Laminate Forming (LOM)

Currently studying the LOM process are Helisys, Huazhong University of Science and Technology, Tsinghua University, Kira, Sparx and Kinergy. In addition to the original LPH, LPS and LPF series of paper products, Helisys also developed plastic and composite materials. HRP series molding machines and molding materials introduced by Huazhong University of Science and Technology have high performance-to-price ratio. Tsinghua University has introduced the SSM series of molding machines and molding materials.

3.3 Selective Laser Sintering (SLS)

The SLS includes DTM, EOS, Beijing Longyuan, Huazhong University of Science and Technology, and Nanjing University of Aeronautics and Astronautics. DTM company launched Sinterstation2000, 2500 and 2500Plus models in 1992, 1996 and 1999 respectively. The model volume of the 2500Plus model has increased by 10% compared with the past. At the same time, the optimization of the heating system has reduced the auxiliary time and increased the speed of forming. Beijing Longyuan introduced the AFS-300 molding machine. Huazhong University of Science and Technology has developed a HRPS-1 type machine for casting middle sand molding and a HRPS-III type molding machine for high polymer powder molding. In terms of materials, DTM has several new products coming out every year. The production of DuraformGF material is more accurate and the surface is smoother. The recently developed elastomeric polymer Somos 201, which has rubber properties and is resistant to heat and chemicals, has been used to create leak-proof flexible parts such as snake tubes, gaskets and door seals on automobiles; with Rapidsteel2 .o Stainless steel powder mold, can produce 100,000 pieces of injection molded parts; Rapidtool2.0 this material has a shrinkage rate of only 0.2%, its parts can achieve high precision and surface finish, almost no subsequent polishing process. DTMPolycarbonate Copper -
Nylon mixed powder, mainly used for making small quantities of injection molds. EOS has developed a new nylon powder material, PA3200GF, similar to DTM's DuraFormGF, which uses this material to produce parts with better accuracy and surface finish.

3.4 Fuse deposition forming (FDM)

The main research FDMs are Stratasys and MedModeler. After Stratasys developed the first FDM-1650 model in 1993, it successively introduced FDM-2000, FDM-3000 and FDM-8000 models. What attracts attention is the FDM-Quantum model introduced by Stratasys in 1998. The maximum shape volume is 600mm x 500mm x 600mm. Thanks to the Magna Drive system, which has an extrusion head, two extrusion heads can be independently controlled at the same time, so the molding speed is five times that of the past. Stratasys partnered with MedModeler in 1998 to develop MedModeler models for hospitals and medical research units, using ABS materials, and in 1999 introduced the Genisys-type improved model that can use polyester thermoplastics - GenisysXs, with a volumetric shape 305mm × 203mm × 203mm. Tsinghua University introduced the MEM model.

Fused wire materials are mainly ABS, synthetic rubber, cast wax, and polyester thermoplastics. In 1998, Swinburm University of Technology in Australia studied a metal-plastic composite filament. In 1999 Stratasys developed a water-soluble support material that effectively solved the problem of difficult or impossible removal of support materials in complex, small holes.

3.5 Others

In 1997, Z introduced the Z-402 model, which uses wax-based starch or epoxy resin as a raw material and sprays the adhesive onto the powder to manufacture parts. In 1998, ProMetal launched the RTS-300 model, which uses steel, steel alloys, nickel alloys, and titanium-niobium alloy powders as raw materials. It also employs the technology of spraying adhesive onto powders to directly and rapidly produce metal parts.

In 1999, 3D System Co., Ltd. developed a ThermoJet Solid Object Printer that uses thermoplastics to achieve higher molding speeds.

In 1998, the New Jersey Institute of Technology proposed a new technique of rapid freeze forming (REP). Pure water was used as the prototype material, and the brine with lower freezing point was used as the support material. The formed parts were then deposited and flash frozen. Since 1998, micro-manufacturing technology has also been an active research direction for RP technology. A US research team has used CAD technology to produce high-density parts with a diameter of only 100 micrometers. Another research group has studied a new micro-fabrication method. Similar to the solid-solidification (SGC) technology, the technology is said to produce molecular-level parts with a layer thickness of only 2 microns.

4. New Developments in Rapid Tooling (RT) and Rapid Manufacturing (RM) Technology

The current rapid molding methods are roughly indirect molding methods and metal direct molding methods. Commonly used rapid molding methods are soft mold, bridge mold and hard mold.

Soft tooling usually refers to a silicone rubber mold. After prototypes made with SLA, FDM, LOM, or SLS techniques are turned into silicone rubber molds, two-component polyurethane is poured into the molds to obtain the desired parts after curing. By adjusting the composition ratio of the two-component polyurethane, the mechanical properties of the obtained polyurethane parts can be made close to those of ABS or PP.

Bridge tooling usually refers to an epoxy resin mold that can be directly injection molded. Compared with traditional injection molds, the cost of using epoxy molds is only a fraction of that of traditional methods, and the production cycle is greatly reduced. The die life is less than the steel die, but it is higher than the silicone die and can reach 1000-5000 pieces, which can meet the needs of small and medium batch production. Ciba Fine Chemicals of Switzerland developed CibaTool, a resin mold series material.

(Table omitted)
Hard tooling generally refers to the manufacture of a metal mold in an indirect manner and the direct machining of a metal mold with rapid forming. Currently, wax or resin models are processed using SLA, FDM, and SLS methods, and investment castings are used to produce metal parts.

There is also the use of SLS methods to select the appropriate molding materials and process casting cavities for casting. The process of making an injection mold or other metal mold using a prototype as a master mold combined with precision casting, and typically, a 3D System Quick Cast, an Express Tool, and the like.

Over the years direct metal forming and rapid tooling technology has focused primarily on selective laser sintering (SLS) to directly make metal molds.

This type of sintered part is usually a low-density porous structure, and can form a metal mold directly after infiltrating the low melting point metal.

The problem of strength and accuracy of parts has always been an insurmountable obstacle. Optomec launched the LENS-50 and LENS-1500 models in 1998 and 1999, respectively. Using steel, steel alloys, iron-nickel alloys, titanium-niobium alloys, and nickel-aluminum alloys as raw materials, the metal is directly deposited and formed using a laser net forming technique. Make this technology a breakthrough. The strength of its metal parts produced exceeds that of traditionally produced metal parts. The precision X/Y plane can reach 0.13mm and the Z direction is 0.4mm, but the surface finish is poor, which is equivalent to the surface finish of the sand casting. DTM also introduced a new sintered material, Rapidsteel 2.0, whose metal powder has not been changed from carbon steel to stainless steel. The infiltrated alloy is changed from brass to bronze and does not require the infiltration of liquid polymer as in the original process. Almost half shortened. EOS has developed DirectStees-VI, a new metal sintered material.

MetLAM, a metal plate for LOM, has been developed. Metal foil can be used as a LOM molding material to directly process the EPS gasification mold for casting, and metal castings can be mass-produced. The Tokyo Institute of Technology has also developed a system for stacking metal molds from sheet metal. There are also Metal Materials ProMetal, RTS-300, etc. used for 3D Printing.

The use of SLA, SLS, FDM, or LOM methods to process wax patterns in investment casting is one of the most important ways to produce metal parts and metal molds. After the special modeling of the prototype surface obtained by rapid sculpting, it is replaced with a wood mold to directly manufacture a plaster or porcelain type, or a transition from a RP prototype to a plaster or ceramic type through a silicone rubber mold transition, and then cast from a plaster or ceramic type. Metal mold. This is also one of the effective methods.

European EAPRR (European Engineering Action) cooperates with Rover Group to study the possibility of direct injection moulding of RP parts. It uses a variety of rapid prototyping processes to directly make Injection Molding inserts for Rover seat adjustment handwheels. The back is lined with epoxy aluminum. Powder to increase mold strength and improve heat dissipation, and then it is installed in the mold frame, the assembled mold is placed on the injection molding machine to produce polypropylene parts. The results are as follows (Table 1).

5. Application and Market of Rapid Prototyping Technology

By 1999, there were 334 rapid prototyping service bureaus, 27 equipment manufacturers, 12 material suppliers, 14 specialized software suppliers, 23 consulting agencies and 51 companies around the world. Education and scientific research institutions. The competition among major equipment manufacturers is becoming increasingly fierce, and its market share is shown in Figure 4. The annual sales volume of rapid prototyping equipment and rapid prototyping service organizations have increased year by year. The service organization in 1999 was 1992.
7.9 times of the year.

Constantly improving the application level of RP is an important aspect of promoting the development of RP technology. Since the RP technology was born, all RP system manufacturers and RP service centers are constantly expanding the application of RP technology. From the first cooperation between 3D and Chrysler, RP technology has been applied in many fields. Its application scope is mainly in design inspection, market prediction, engineering testing (stress analysis, wind tunnel, etc.), assembly testing, Mold manufacturing, medicine, aesthetics and so on.

Figure 5.6 shows the application of RP technology. RP technology is most widely used in the manufacturing industry, reaching 67%, illustrating the enormous role of RP technology in improving product design and manufacturing levels.

Recently, the application of RP has emerged as follows:

1) Use RP technology for sheet metal forming. This technology uses the RP model to make a forming mold and forms a small batch of metal parts through a hydraulic press.

2) More complex functional tests, mainly applied to fluid and gas flow tests. Since flow analysis is one of the most complex analyses in engineering analysis, the determination of flow parameters and design parameters by means of actual tests is a common method.

Includes RP prototypes using high temperature materials for functional testing of engines and pumps.

3) in biological and medical applications (Figure 7): A US research team uses RP technology to produce artificial lungs and artificial hearts, and another research team uses a kind of biological material to build biological tissues on small-spot laser SLA systems. Muscle and so on. There is also the use of RP technology to help develop new medical devices.

4) In the application of art, the use of RP technology to establish Buddha statues and digital sculpture.

5) Application in the molding of metal and ceramic parts.

6) Make colored parts. At present, it has been possible to produce a production with two colors (such as a dental mold).

6. Prospects of RP Technology

After more than ten years of development, RP technology has made great strides in both equipment and materials. However, due to the high cost of this technology, the precision, strength, and durability of the manufactured parts cannot satisfy the requirements of users and temporarily hindered them. The promotion and popularization of RP technology. In addition, in recent years, Cnc Cutting machine tools have also been making strides forward. On the one hand, prices have dropped dramatically. On the other hand, high-speed, high-precision Cnc Machine tools have come out, shortening the number of parts and improving the accuracy and surface quality. Therefore, many companies use CNC cutting machine tools to rapidly manufacture metal or non-metal molds and parts, which pose new challenges to RP technology. However, in the formation of complex, hollow parts, CNC cutting machine can not replace the RP technology. This kind of design and production mode that is directly transferred from the concept design to the product is necessarily the mainstream of manufacturing technology in the 21st century. With the advancement of technology, RP technology will continue to advance with great strides and will become the basic technology and equipment for many design companies, manufacturing companies, research institutions, and educational institutions.

From the above RP technology development status, the trend in the next few years is mainly:

1) Improve the speed, control accuracy and reliability of the RP system, optimize the equipment structure, use components with high cost performance and long life, make the system more concise, more convenient operation, higher reliability and faster speed. The development of models with different grades and different uses is also an aspect of the RP system development. For example, on the one hand, development of high-precision, high-performance models to meet the user's requirements for parts of the size, shape and surface quality of higher or special requirements. On the other hand, we developed a concept machine that is specially designed for inspection design and simulation of product visualization, but does not require high dimensional accuracy and surface roughness.

2) Improve data processing speed and accuracy, research and develop direct CAD data slicing methods, reduce data processing volume and data defects and contour distortion caused by the STL format conversion process.

3) Molding materials with low research and development cost, easy molding, small deformation, high strength, durability and no pollution. The existing materials, especially functional materials, are reformed or preprocessed to make them suitable for the technological requirements of RP technology. Starting from the characteristics of RP, combined with various application requirements, the development of new RP materials, especially composite materials, such as nano Materials, heterogeneous materials, composite materials that are difficult to make by other methods, etc. Reduce the cost of RP materials and develop new, cheaper materials.

4) Develop new molding energy sources. In the aforementioned mainstream molding technologies, SLA, LOM, and SLS all use laser as an energy source, and laser systems (including lasers, coolers, power supplies, and external light paths) are expensive and maintenance costs are high and transmission efficiency (output laser energy/input electric energy) is relatively high. Low, affecting the cost of parts. Research on new shaped energy is also an important direction of RP technology.

5) Research and develop new molding methods. Over the past decade, many researchers have developed dozens of molding methods that are basically based on the idea of three-dimensional planarization-discrete-stacking. This method still has many deficiencies. In the future, it is possible to study the rapid prototyping method integrating “stacking” and “cutting”, that is, combining RP with CNC machine tools and other traditional processing methods to improve the performance and accuracy of the parts. ,reduce manufacturing cost. It is also possible to extend from the RP principle to generate some new rapid prototyping methods.
6) Continue to study rapid tooling (RT) and rapid manufacturing (RM) technologies. On the one hand, research and development of RP parts surface treatment technology to improve surface quality and durability; the other side research and development and injection molding technology, precision casting technology combined with new ways and new processes, rapid and economical manufacturing of metal molds, metal parts and plastic Pieces.
7) In terms of application, through the improvement of existing RP systems and the development of new materials, it can economically produce directly usable molds, industrial products and consumer goods; and create artificial organs for the treatment of diseases.